class_docstr: BaseTransform is a base class that defines a pair of complementary
  coordinate mapping functions in both python and GLSL.
  
  All BaseTransform subclasses define map() and imap() methods that map
  an object through the forward or inverse transformation, respectively.
  
  The two class variables glsl_map and glsl_imap are instances of
  shaders.Function that define the forward- and inverse-mapping GLSL
  function code.
  
  Optionally, an inverse() method returns a new transform performing the
  inverse mapping.
  
  Note that although all classes should define both map() and imap(), it
  is not necessarily the case that imap(map(x)) == x; there may be instances
  where the inverse mapping is ambiguous or otherwise meaningless.
code: def __repr__(self):
      return "<%s at 0x%x>" % (self.__class__.__name__, id(self))
  
imports: from __future__ import division
  from ..shaders import Function
  from ...util.event import EventEmitter
  from .chain import ChainTransform
label_desc: Use image node_id 13 for calling the BaseTransform obj's underlying member method code with example usage: obj.__repr__() and returns: unknown